<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
</head>
<body>
  <div id="app">
    <ul>
      <li v-for="(item, index) in letters" :key="item">{{item}}</li>
    </ul>
  </div>
  <script src="../js/vue.js"></script>
  <script>
    const app = new Vue({
      el: '#app',
      data: {
        letters: ['a','b','c','d','e']
      }
    })
  </script>
</body>
</html>